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Sucessfully submitted for the award of Master of Philosophy (M.Phil) to the Dublin Institute of Technology, 2009.

Abstract

This research work adapted and applied a recently developed method for assessing epiphytic lichen species diversity to the Irish semi-natural woodlands of Knocksink Wood Nature Reserve, Enniskerry, County Wicklow. The study focused on the differences that arise in relation to acidophilous oak woodland (Blechno-Quercetum petraeae) versus ash-hazel woodland (Corylo-Fraxinetum). The research also addressed differences in relation to the mixed oak-ash-hazel woodland located in Knocksink Wood and the neighbouring woodland at the Powerscourt Waterfall. The frequency of occurrence of lichen species on a defined portion of tree bark was used as an estimate of diversity and to evaluate the degree of environmental stress on the sensitive lichen community. In total 52 lichen taxa were recorded on the trees in the woodlands in Knocksink Wood. The sequence of lichen numbers recorded per tree genera in Knocksink Wood was oak > ash > willow > beech > sycamore. The oak trees in the oak woodland were richer in lichen flora on the trunk area (35 lichen taxa) than the ash trees in the ash- hazel woodland (24 lichen taxa). Very low lichen diversity (LD) values were recorded in the oak woodland and the oak-ash-hazel woodland and a higher LD was recorded in the ash - hazel woodland. The overall pattern for Knocksink demonstrated low diversity of epiphytic lichens. Based on the recorded epiphytic lichens and LD values generated, the quality of the natural environment in Knocksink Wood was assessed as relatively low. This had been further corroborated by comparison with the epiphytic lichen flora of other broadleaf woodlands in Ireland. The unique setting of Knocksink Wood in a sheltered river valley and human input were identified as the main factors influencing development of epiphytic lichens in Knocksink Wood. The most significant parameters influencing epiphytic lichen development at trunk level in the woodlands at Knocksink were tree species, age profile and diversity of woodlands, bark properties and light availability, past woodland management and contemporary human input. The results of this research suggest that the European guideline for mapping lichen diversity developed in mainland Europe has applicability in the Irish setting and can detect differences between woodland habitats in terms of epiphytic lichen distribution. This research advances understanding of the factors that drive the sensitive and dynamic patterns observed for epiphytic lichen abundance and distribution in Irish broadleaf woodlands and forms a base for future environmental monitoring studies.